They already got their legacy. They (usually) already got their money. The added stress, crazy hours, and risk to the reputation probably just isn’t worth it when they could take a booth job for similar money.

I was always a huge Bob Sanders fan. He did succeed with a SB, two first team all-pros, and a DPOY award, but his prime/career was cut horribly short from injuries. He only played above 6 games twice in his career, and racked up all those accolades listed above in those two seasons alone.